1. Field of the Invention
The present invention relates generally to a watertight RF connector of a coaxial cable, and more particularly to a watertight RF connector having an axial barb seal.
2. Description of the Related Art
A coaxial cable, which is used to transmit radio frequency (RF) signals, is a cylindrical transmission line made up of an inner conductor and a tube-shaped outer conductor separated by a dielectric spacer. Coaxial cables are connected or terminated using an RF connector. The RF connector has an inner conductor and tube-shaped outer conductor, which connect to the respective conductors of the cable.
It is sometimes required to place coaxial cables and RF connectors outdoors. The RF connectors must therefore be adequately weatherproofed so as to prevent water and moisture due to rain and humidity from entering the connector bodies and adversely affecting the components, within the connectors and cables.
Most conventional RF connectors rely on a mating interface connector to prevent moisture ingress. An improved connector will use O-rings to seal the interface between the dielectric spacer and outer conductor of the connector. This will prevent moisture ingress along the axis of connector. Although the moisture seal provided by the O-ring is effective, the O-ring is an additional component resulting in a more complex and costly assembly.
Attempts have therefore been made to eliminate the O-ring from the construction of the connector by providing ring-shaped radial barbs that project from the conductors and press fit into the spacer. However, radial barbs alone are not sufficient to provide a reliable moisture seal over a wide enough temperature range. That is, most dielectric materials (e.g., Teflon) suitable for manufacturing spacers of RF connectors have a larger coefficient of expansion than the conductive material (e.g., brass) used to form the outer conductor portion of the connector. At colder temperatures the spacer therefore shrinks away from the outer conductor, thereby compromising the intended seal between the outer conductor and the spacer.
It is an object of the present invention to effectively seal an RF connector from water and moisture without the use of an O-ring.
This object is fulfilled by providing a connector with a combination of an outer radial barb projecting radially inwardly and an axial barb projecting axially from the outer conductor into the dielectric cylinder. When the dielectric cylinder attempts to shrink away from the outer conductor during colder temperatures, the outer radial and axial barbs work in cooperation to oppose the force of thermal contraction of the cylinder to thereby ensure that the moisture seal of the connector is maintained.